The encoding functionality in XMLEncoderAdapter would throw an exception

when encountering a floating point value, indicating that the value was not

XML serializable.  This has been corrected by adding special handing for

floating point values, analogous to how other data types are handled.

Added new unit tests to exercise both the JSON and XML encoder adapters.
Encoding is attempted on a variety of data types.  Prior to the fix, the
XML-based test would fail due to the presence of floating point data types.